EventIndex: Cancel the crawler early after a message request.
EventIndex: Cancel the crawler early after a message request.

If we're cancelling the crawler nowadays this means that we're likely
deleting the index. Processing these messages is wasted effort in that
case so break early.

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk